Extreme pressure lubricant



Patented Mar. 26, 1940 UNITED STATES PATENT OFFICE EXTREME PRESSURE LUBRICANT Franz Rudolf Moser and Dirk Roelof Nijk, .Amsterdam, Netherlands, assignors to Shell Development Company, San Francisco, Calif... a corporation of Delaware No Drawing. Application August 2, 1937, Serial No. 156,958. In the Netherlands August 29,

11 Claims.

This invention relates to lubricants suitable" seizure and scoring of metals which are in motion relative to each other under very high pressures. Most of the substances heretofore suggested contain halogen, sulfur or phosphorus in a form conducive to corrosion. The thought generally prevailed that these elements give rise to a chemical reaction to form products which keep the metals separated when the oil film gives way un der excessive pressures. It was reasoned that since a chemical reaction is essential to the working of an extreme pressure lubricant, a certain amount of corrosion is indispensable for the activity of extreme pressure substances.

It has further been proposed to use oxyhydrocarbons such as fatty acids, cresols, phthalic acid, etc., for the purpose of enhancing the power of extreme pressure substances. However, these oxyhydrocarbons, when used by themselves, have little, if any, effect in the matter of inducing extreme pressure properties in mineral oils. .It is the purpose of this invention to provide extreme pressure lubricants which are free from ccri'osiveness and which for their effectiveness apparently do not rely, or rely only partially, on a chemical reaction between the metals and the extreme pressure substances.

We have discovered that aromatic and hydroaromatic compounds built up of at least two fi-carbon rings, standing in close proximity to. each other and containing at least two hydroxyl radicals separated from the rings by not more than 1 carbon atom, i. e.', they may be attached directly to the ring as in phenols, or may be part of carbo-hydroxyl groups as in benzoic acid or benzyl alcohol, show good extreme pressure qualities when added to lubricating oils in quantities substantially above 1%.

While the presence of two of the hydroxyl radicals is suflicient to impart to the polycyclic compounds extreme pressure properties, additional The compounds of our invention are non-corrosive towards steel, bronze and various bearing metals and in many instances have positive anticorrosive properties, particularly so if they possess two or more carboxyl radicals. the compounds are structurally compact, they are also highly resistant to thermal decomposition at the elevated temperatures normally encountered in the lubrication of internal combustion engines and are therefore especially valuable for use in crankcase lubricants for internal combustion engines.

Due to the fact that our compounds possess two or more hydroxyl or carboxyl'radicals they have high boiling temperatures, and most .of them are substantially non-volatile, .Thisis of obvious advantage in lubricating oils .to be used in internal combustion engines.

The solubility of our compounds in hydrocarbon oils is quite low andtherefore they are usually used in the form of suspensions rather than solutions. Suspensions may be prepared in any suitable manner, as by dispersing the compounds in the lubricating oil with the aid of a colloid mill,

or by dissolving them in a mutual solvent, etc.

Substances having a stabilizing effect on the suspension so produced, such as small quantities of fatty acids of the type of stearic acid, may be added to advantage. preserve the suspension, such substances have frequently the additional eifect of enhancing the extreme pressure properties of our compounds, particularly at elevated temperatures, whenthe suspensions tend to become unstable.

It has been stated hereinbefore that the two or more'fi-carbon rings of our compounds should stand in close proximity to each other. By this "we mean that the carbocy'clic rings should preferably be separated from each other by a chain or chains of not more than two atoms of an element normally capable of firmly linking 6-carbon rings to produce stable compounds, said element having an atomic number below 17 Thus compounds containing two or more 6-carbon rings which are separated by two or less carbon or nitrogen atoms, or by a single atom of the group consisting of oxygen, sulfur and phosphorus, not

forming part of the ring, or which are advantageously linked directly without an intermediate atom as in diphenyl, or by common carbon atoms as in naphthalene, are known to be very stable in the absence of other unstable linkages or radicals. While many compounds are known in which the rings are separated by other elements, having atomic numbers above 16 capable of link- If, furthermore,

Owing to their power to Y ing 6-carbon rings, such as As, Sb, Hg, Pb, etc., we have found that such compounds, although sumciently stable for many purposes are not sufflciently stable to be of practical use in lubrication, particularly at high temperatures or in the presence of moisture, nothwithstanding that all of them exhibit extreme pressure properties, provided they have the necessary hydroxyl radi-' cals; and still other compounds in which the link is formed by elements shaving atomic-numbers below 17, other than those enumerated above,

such as Mg, A1, Si, are known'to be extremely unstable, some of them igniting in contact with air, and others rapidly hydrolyzing in contact with water. l

Derivatives containing the necessary hydroxyl radicals of diphenylethane, diphenylmethane, tri-.

' phenylmethane, dlphenyl, naphthalene, tetraline,

anthracene, phenanthrene, picene, chrysene, acridine, phe'nacine, diphenyloxlde, dinaphthyloxide, diphenylsulflde, dinaphthylsulflde, carbazol, azobenzol triphenylphosphine, or homologues of these compounds are examples of suitablecompounds.

In addition, the rings may contain short aliphatic side chains, relatively long side chains of more than 2 carbon atoms being very'undesirable as they greatly lower the thermal stability-of our compounds. h I

The presence of polar radicals other than hydroxyl of the type described in our compounds may be permissible but is usually of little advantage and in many instances of decided disadvantage For instance amino radicals frequently reduce the resistance of our compounds toward oxidation, halogens tend to make them corrosive,

7 nitro radicals lower the thermal stability, etc.

' The quantity of our compounds required to 1111- (part to mineral lubricating oils high pressure resisting properties normally varies between about 1 to 10%. I

In the following examples, which illustrate our invention, results are shown of tests, made in the Boerlage Four-ball apparatus described in Engineering, July 14, l93 3,-with a straight mineral lubricating oil and blends thereof with various compounds of the group herein described.

Example I A 4% suspension of a methylene dib'etanaphthol in a Venezuelan brightstock gave a welding pressure of 300 kg., whereas the unblended oil permitted welding at 150 kg.

Example II A suspension of 4% of a 1 hydroxy naphtlfoic acid in the oil of Example I likewise gave" a welding pressure of 300kg.

Example .111

The family of diphenyl methanederivatives provides a large number of suitable compounds which may be obtained by condensing polyphenols, as

hyde and'20 parts of an 8% aqueous hydrochloric Q acid is allowed to stand for several hours,- during ghich time a precipitate of methylene diresorci' e IV, in a 4% suspension in the lubricating oil of derivatives of triphenyl methane, may be obformic acid, suspended in the lubricating oil of Example I raised pable of improving the load carrying capacity of of resorcine,

is formed, which is filtered an and recrystallized -from ethyl alcohol. The product obtained conofmicroscopic crystals. A 4% suspension thereof in the brightstock of Example I raised the welding pressure to 500 kg. All parts are by 5 weight.

Example IV- 180 grams of salicylic acid are heated on a steam bath for 40 hours with 90 grams of a 30% aqueous formaldehyde solution and 640 milliliters concentrated hydrochloric acid. The crystalline salicylic acid is slowly converted to-a sandy powder containing methylene disalicylic acid, which is washed with water to remove the free hydrochloric acid, dissolved in dilute ammonia, filtered and reprecipitated with dilute sulfuric acid.

' A 4% suspension of the product in the lubricating oil of Example I gave a welding pressure of 600 kg. I

Example V a Methylene digallic acid, obtained in a manner similar to the procedure described in Example Example I gave a-welding pressure of 500 kg.

Example VI Another large class of suitable compounds known asthe rosolic acids or aurines, which are tained by condensing phenols or carboxyl phenols with oxalic acid in the presence of a condensing agent such .as sulfuric acid, zinc chloride, etc. A a 4% suspension ofaurlneor pararosolic acid raised the welding pressure in the lubricating oil of Example I to 400 kg. 1

Example VII 7 Likewise a 4% suspension of aurine tricar= boxylic acid prepared from salicylic acid and an oxidant, e. g. nitrous acid, raised the welding pressure to 500 kg. r

.E'mm ze VIII 4% resaurine, prepared from resorcine and the welding pressure to 600 kg.

Example IX A further large group of useful compounds cathe fllms of lubricating oils to which they are added, comprises the group of azo compounds obtained from 'diazotized benzidine, in which both amino radicals are diazotized. Many of these compounds are exceedingly stable at the elevated temperatures to which lubricants may be exposed in the normal course of their usage.

Thus, when coupling 1 mol diazotized benzldine with 2 mols phenol under conditions .to produce the azo compound, the product so obtained, added to the lubricating oil of Example I in an amount of 4%. raised the welding pressure of the latter to 300 kg. A 4% suspensionof the product of similarly coupling diazotized benzidine with resorcine, had a welding pressure of 600 kg. A similar suspension of a condensation product of 1 mol diazobenzidine with 2 mols salicylic acid had awelding pressure of 500 kg., and a4% suspension of an ,az'o compound-produced from diazobenzidine and dibetanaphthol had a welding pressure of 600+ kg.

Other hydroxy aromatic compounds-such as those enumerated in Example 111 may al'sobensed for coupling with the diazobe'nzidine, whereby 75 powerful extreme pressure compounds are produced.

We claim as our invention:

.1. A non-halogenated compounded lubricantcomprising a mineral lubricating oil and from 1 to of an organic compound possessing at least two isocyclic fi-carbon rings in close proximity, to each other and at least two hydroxyl radicals separated from the rings by not more than 1 carbon atom, said compound being stable under the conditions normally encountered in the lubrication of internal combustion engines and free from alkyl radicals of more than two carbon atoms and radicals-tending to induce corrosion.

2. A non-halogenated compounded lubricant comprising a mineral lubricating oil and from 1 to 10% of an organic compound possessing at least two isocyclic 6-carbon rings separated from each other by at least 1 link consisting ofless' than 3 carbon atoms, said compound having at least 2 hydroxyl radicals separated from the rings by not more than 1 carbon atom, being stable at the temperature normally encountered in the lubrication of internal combustion engines and free from alkyl radicals of more than two carbon atoms and radicals tending to induce corrosion.

3. A non-halogenated compounded lubricant comprising a mineral lubricating oil and from 1 to 10% of an organic compound possessing at least two isocyclic 6-carbon rings separated from'each other by at least 1 link consisting of less than 3 nitrogen atoms, said compounds having at least 2 hydroxy1 radicals separated from the rings by not more than 1 carbon atom, being stable under the conditions normally encountered in the lubrication of internal combustion engines and free from alkyl radicals of more than two carbon atoms and radicals tending to induce corrosion. a 4. A non-halogenated compounded lubricant comprising a mineral lubricating oil and from 1 to 10% of an organic compound possessing at least two isocyclic 6-carbon rings directly coupled and at least 2 hydroxyl radicals separated from the rings by not more than 1 carbon atom,

being stable under the conditions normally encomprising a mineral lubricating oil and from 1 to 10% of an organic compound possessing at least'two isocyplic G-carbon rings in close proximity to each other and at least 2 hydroxyl radicals directly attached to the rings, said compound being stable under the conditions normally encountered in the lubrication of internal combustion engines and free from alkyl radicals of more than two carbon atoms and radicals tending to induce corrosion. L

' 6. A non-halogenated compounded lubricant comprising a mineral lubricating oil and from 1 to 10% of an organic compound possessing at least two isocyclic 6-carbon rings in close proximity to each other and at least 2carboxyl radicals directly attached to the rings-said compound being stable under the conditions norto 10% methylene digallic acid.

10. A non-halogenated compounded lubricant comprising a mineral lubricating oil and from 1 to 10% of an organic compoundpossessing at least two isocyclic 6-carbon rings separated from each other by at least one link consisting of less than 3 atoms having atomic numbers below 17 and capable of firmly linking 6,-carbon rings to produce a stable compound, and said compound having at least 2 hydroxyl radicals separated from the rings by not more than one carbon atom, being stable under the conditions normally encountered in the lubrication of internal combustion engines and free from alkyl radicals of more than two carbon atoms and radicals tending to induce corrosion.

, 11. A non-halogenated compounded lubricant comprising a mineral lubricating oil and from 1 to 10% of an organic compound possessing at least two isocyclic six carbon rings in close proximity to each other, at least one carboxylic group and at least one hydroxy group attached directly to a ring, said compound being stable under the conditions normally encountered in the lubrication of internal combustion engines, and being free from alkyl radicals of more than two carbon atoms and radicals tending to induce corrosion.

FRANZ VRUDOLF' MO'SER. DIRK ROELOF max. 

